German Published Patent Application No. 197 35 624 describes a method for the non-contact transmission of electric power from a medium-frequency current source having a medium frequency fM to one or more moving consumers via a transmission line, and from transformer heads, allocated to the moving consumers, having a downstream matching controller for adjusting the power received from the transmission line, the transmission line being fed from the medium-frequency current source with a medium-frequency current that is constant in its effective value during the power transmission.
The matching controller converts the medium-frequency current, injected from the transformer head, into a DC voltage. As described in FIGS. 3, 7a and 7b and the associated description of German Published Patent Application No. 197 35 624, switch TS is operated synchronously with respect to the characteristic, and with double the frequency of the input current of the matching controller. However, an important disadvantage is that this high switching frequency 2fM results in high switching losses. Another disadvantage is that the synchronous principle can no longer be maintained when using a plurality of asynchronously operating feed-ins for supplying a matching controller.
In the case of German Published Patent Application No. 197 35 624, a relay is used which, after the matching controller is switched in, goes into the blocking state with low voltage. Upon switch-off or in response to a short-circuit in the region of this low voltage, the relay returns again to the conductive state. It may be disadvantageous that the relay is subject to mechanical wear, and therefore may lead to an accident. It may also be disadvantageous that in German Published Patent Application No. 197 35 624, in case of an emergency, a dangerously high voltage may occur at the consumer, which may lead to accidents.
Therefore, it is an object of the present invention to increase safety when working with a matching controller, e.g., to avoid the danger of fire in the event of an emergency or during unusual operating conditions.